The problem of using a best-effort network for online games

THE PROBLEM OF USING A BEST-EFFORT NETWORK FOR ONLINE GAMES

NIME WORKSHOP. IEEE CCNC 2014

Index I. Real-time services on

the Internet

II. The two problems

III. Adapting the network

Real-time services - Real-time services are being widely used:

VoIP, video conference, online gaming

Real-time services In this presentation, we will focus on online gaming. Why?

Popularity of online games

The approach Client-server architecture

- Consistency of the game

- Cheating avoidance

- Billing

How does it look? (On the packet level)

40 50 60 70 80 90 100 110bytes

0 10 20 30 40 50 60 70ms

40 50 60 70 80 90 100 110bytes

0 10 20 30 40 50 60 70ms

40 50 60 70 80 90 100 110bytes

0 10 20 30 40 50 60 70ms

Unreal Tournament

Counter Strike I

Quake III


the Internet



- Efficiency problem: Sending very frequent updates containing small volume of information is not efficient

- Not everybody has fast connections with excess bandwidth

- Quality problem: Using a best effort network for a real-time service

- Online games present very stringent real-time requirements: players are really difficult to satisfy

- We need to measure quality, in terms of network parameters.

Still there are problem(s)

Efficiency problem If I have to send a big file, I divide it in chunks of 1500 bytes, and I may have an efficiency of 97%

One IPv4/TCP packet 1500 bytes

η=1460/1500=97%

IPv4 TCP

Efficiency problem But real-time services cannot wait. They need information every (e.g.) 20 ms, so efficiency gets really bad (33%):

One IPv4/UDP/RTP VoIP packet with two samples of 10 bytes

η=20/60=33%

codec G.729a, 2 samples IPv4 UDP RTP

Quality problem: QoE for games

S. Möller, S. Schmidt, and J. Beyer, “Gaming Taxonomy: An Overview of Concepts and Evaluation Methods for Computer Gaming QoE,” in International Workshop on Quality of Multimedia Experience, QoMEX, 2013, pp. 1–6.

- More experienced players demand more!

User impact

M. Suznjevic, L. Skorin-Kapov, and M. Matijasevic, “The Impact of User, System, and Context factors on Gaming QoE a Case Study Involving MMORPGs”, The 12th Annual Workshop on Network and Systems Support for Games, 2013., p. 6

- Player’s surrounding s (other players) have an impact on QoE scores!

Context impact

M. Suznjevic, L. Skorin-Kapov, and M. Matijasevic, “The Impact of User, System, and Context factors on Gaming QoE a Case Study Involving MMORPGs”, The 12th Annual Workshop on Network and Systems Support for Games, 2013., p. 6

- Difference between game genres

System impact - genres

0

50

100

150

200

250

FPS RPG RTS

Tolle

rate

d o

ne

way

de

lay

[ms]

Game genre

- Major parameters: Delay, jitter, packet loss

- Fixed networks - Stable

- Very low packet loss and jitter

- Delay is still an issue

- Mobile networks - Huge growing market

- Worse network conditions

- Variation of network parameters

Network side

- Client side prediction - QoS-enabled home devices (traffic

prioritization) - Traffic shaping - Dedicated networks - Geographical server distribution - Optimization of server locations - Lag compensation mechanisms

(moving server time into the past)

How do we fight network delay?


the Internet



- Different solutions in order to enhance the network support for online games

- Traffic optimization

- Traffic prioritization

- Latency reduction methods

Adapting the network

VoIP optimization - Voice trunking between two

offices:

VoIP optimization - Savings of 50% are achievable

.

.

.

.

.

.

Context Context

IP Network

MUX+COMP DEMUX+DECOMP

Real-Time Tunneling-Compressing-Multiplexing Real-Time

.

.

.

.

.

.

VoIP optimization - RFC 4170 (2005) deploys this,

also compressing the header

PPP

PPP Mux

ECRTP

payload

IP

UDP

RTP...

ECRTP

payload

L2TP

IP

One IPv4/UDP/RTP VoIP packet with two samples of 10 bytes

η=20/60=33%

Five IPv4/UDP/RTP VoIP packets with two samples of 10 bytes

η=20/60=33%

saving

VoIP

One IPv4 TCMTF Packet multiplexing five two sample packets

η=100/161=62%

40 to 6-8 bytes compression

Optimization - A trade-off appears:

- Efficiency problem: we are improving it, since we are saving bandwidth and reducing pps

- Quality problem: We are adding an additional delay

Game traffic optimization - Can we do the same with games?

- Is there any scenario where a number of game traffic flows share the same path?

Game optimization scenarios - Between the network provider

and the game company

ISP networkInternet

Evolved NodeBeNB

Internet Router

(ISP)

xDSL router

xDSL router

DSLAM

BRAS

Home network with a number of users (e.g. Internet Café, access

shared by neighbours)

Individual DSL

Network of the service

provider

Internet Router

(Service provider)

Application

serverDSLAM 2

LTE access network

ISP aggregation

network

Serving

Gateway

ISP aggregation

network

MUX/DEMUX

Game optimization scenarios - The end user (e.g. internet café)

deploys the multiplexing

ISP network InternetTransport network

Internet Router

DSLAM BRAS



Individual DSL

xDSL routerWith multiplexer

embedded

xDSL routerWithout multiplexer

IETF proposal: TCM-TF Tunneling, Compressing and Multiplexing Traffic Flows

draft-saldana-tsvwg-tcmtf-05

draft-suznjevic-tsvwg-mtd-tcmtf-02

IP IP IP

No compr. / ROHC / IPHC / ECRTP

PPPMux / Other

GRE / L2TP

IP

Compression layer

Multiplexing layer

Tunneling layer

a) TCRTP

Network Protocol

UDP

RTP

payload

UDPTCP

payloadpayload

ECRTP

PPPMux

L2TP

IP

IP

UDP

RTP

payload

b) TCMTF

MPLS

Efficiency improvement IPv4, IPv6


Four IPv4/UDP client-to-server packets of Counter Strike

One IPv4/TCM packet multiplexing four client-to-server Counter Strike packets

η=1460/1500=97%

η=61/89=68%

η=244/293=83%

One IPv4/UDP server-to-client packet of Counter Strike with 9 players

η=160/188=85%

saving

One IPv4/UDP/RTP packet of VoIP with two samples of 10 bytes

η=20/60=33%

FPS optimization


Three IPv6/UDP client-to-server packets of Counter Strike

One IPv6/TCM packet multiplexing three client-to-server Counter Strike packets

η=1440/1500=96%

η=61/109=56%

η=183/246=74%

One IPv6/UDP server-to-client packet of Counter Strike with 9 players

η=160/208=77%

saving


η=20/80=25%

0%

10%

20%

30%

40%

50%

60%

Quake 2 UnrealTournament

Counter Strike1

Quake 3 EnemyTerritory

Counter Strike2

Halo 2 Quake 4

Bandwidth saving IPv4 IPv4 10 ms 5 players

IPv4 10 ms 20 players

IPv4 reached

IPv4 theoretical

FPS optimization

MMORPG optimization Can this be adapted to MMORPGs?

- Higher savings, due to the use of TCP (with a lot of ACKs)

Seven IPv4/TCP client-to-server packets of World of Warcraft. E[P]=20bytes

One IPv4/TCMTF packet multiplexing seven client-to-server WoW packets

η=80/360=22%

η=80/175=45%

saving

TCP ACKs without payload

MMORPG optimization

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

10 20 30 40 50 60 70 80 90 100

BS

period (ms)

TCMTF Bandwidth Saving, TCP/IPv4, World of Warcraft

100 players

50 players

20 players

10 players

tm

THANK YOU!

[email protected] [email protected]

Extra slides

The network is the part that I do not control

- Big amount of data in my hard disk (size of WoW folder)

- Small packets (interactivity requires frequent updates)

The approach

The two problems - Efficiency problem

- If I use IPv6 (the next version of the protocol, with a huge number of different addresses), the efficiency only drops to 96%


η=1440/1500=96%

IPv6 TCP

The two problems - Efficiency problem

- But for real-time services it becomes even worse: only one byte out of four is useful information!


η=20/80=25%

codec G.729a, 2 samples IPv6 UDP RTP

- TCP is sometimes used for games (usually MMORPGs)

- Delayed acknowledgments

- Nagle algorithm

- A lot of “pure” ACK packets

System impact - protocols

Protocol MMORPGs

TCP

World of Warcraft, Lineage I/II, Guild Wars, Ragnarok Online, Anarchy Online, Mabinogi

UDP

EverQuest, City of Heroes, Star Wars Galaxies, Ultima Online, Asherons Call, Final Fantasy XI

TCP/UDP Dark Age of Camelot

VoIP optimization - We merge the packets and make

them share the header:

1 flow

2 flows

3 flows

Game optimization scenarios - The game company places a

multiplexer in the ISP network

ISP network Internet

Evolved NodeBeNB

Internet Router

(ISP)

xDSL router

xDSL router

DSLAM

BRAS



Individual DSL

Network of the service

provider

Internet Router

(Service provider)

Application 1

server

Serving

GatewayLTE access network

MUX/DEMUX of the Service

Provider, hosted by the ISP

MUX/DEMUX

Application 2

server

ISP aggregation

network

ISP aggregation

network

VoIP optimization - RFC 4170 savings (50%):

70%

85%

100%

0%

10%

20%

30%

40%

50%

60%

1234567891011121314151617181920

prob. of reduced headerNumber of calls

TCMTF Bandwidth Saving, RTP/UDP/IPv4 voice G.729a, 2 samples per packet

Significant savings (Counter Strike)

0%

5%

10%

15%

20%

25%

30%

35%

5 10 15 20 25 30 35 40 45 50

BS

period (ms)

Bandwidth Saving

20 players

15 players

10 players

5 players

FPS optimization

- The same problems we can find in VoIP.

- Instead of having two users talking at the same time, we have the “shooting around the corner” problem.

Shooting around the corner

VoIP

Jack Wang

Answer

Question

Network delay scheme

time

Are you there?

“Shooting around the corner”

Jack Wang

Wang

Online games


Jack

Wang: Dead

Wang

Wang

Online games


Jack Wang

Wang: Dead ¡¡¡ #%$& !!!

Online games

Online games “Shooting around the corner”

Jack Game server Wang

Position 1

Position 2

Shot Wang DEAD

Network delay scheme

time

A period is defined, and all the packets arrived are compressed and multiplexed

PE

. . .

. . .

. . .

. . .

Native

traffic

Multiplexed

traffic

PE PE PE

Game traffic optimization

0%

10%

20%

30%

40%

50%

60%

Quake 2 UnrealTournament

Counter Strike1

Quake 3 EnemyTerritory

Counter Strike2

Halo 2 Quake 4

Bandwidth saving IPv6 IPv6 10 ms 5 players

IPv6 10 ms 20 players

IPv6 reached

IPv6 theoretical

Multiplexing

The problem of using a best-effort network for online games

Technology

Transcript of The problem of using a best-effort network for online games